γH2AX expression in cytological specimens as a biomarker of response to radiotherapy in solid malignancies

Abstract

Many anticancer treatments, including radiotherapy, act by damaging DNA and hindering cell function and proliferation. H2AX is a histone protein directly associated with DNA that is phosphorylated to produce γH2AX that accumulates in foci in an early response to DNA double‐strand breaks, the most deleterious lesion caused by anticancer therapy. This study reports a γH2AX detection assay that has the potential to be used as a biomarker of response to guide cancer treatment. γH2AX immunostaining was applied to tumour cell specimens obtained using fine needle aspiration (FNA). Liquid‐based cytology and direct smear cytology methods were evaluated and immunostaining protocols established using FNA samples from five cancer patients. The assay was then applied to three patients before and after radiotherapy. Results demonstrate induction of γH2AX foci following treatment, persisting for as long as one week after therapy. Immunostaining for γH2AX has been successfully applied to FNA samples, providing an opportunity to evaluate γH2AX as a treatment response marker in cancer. Diagn. Cytopathol. 2016;44:141–146. © 2015 The Authors Diagnostic Cytopathology Published by Wiley Periodicals, Inc.

Superresolution light microscopy shows nanostructure of carbon ion radiation‐induced DNA double‐strand break repair foci

“…Our findings challenge the belief that each γH2AX focus represents one DSB and thus may have profound consequences for the interpretation of radiobiology based on focus quantification. For example, γH2AX focus quantification has been used to assess the risk of exposure to ionizing radiation during clinical computed tomographic scans (59–62) and to estimate the dose during radiotherapy (63–65) or in case of radiation accidents (66). Infrastructures for high‐throughput biodensitometry screening after a radiologic event have been developed based on the γH2AX assay (67), and the European Biodosimetry Network is conducting large studies to evaluate the use of γH2AX focus quantification as a risk assessment tool in such cases (68).…”

Imaging the DNA damage response with PET and SPECT

“…The resulting protein, known as γH2AX, forms foci (Fig. 4 [ 54 ]) containing hundreds of copies (measuring up to 40 Mbp) [ 55 ] around each individual break site. Here, γH2AX is involved in the recruitment of most of the other DNA repair proteins discussed above, whereupon it promotes re-joining of DNA remnants [ 56 , 57 ].…”

“…4 Immunostaining of fine-needle aspiration tumour specimens from a patient with non-Hodgkin’s lymphoma deposits reveals the appearance of γH2AX (green) and 53BP1 foci within the nucleus (DAPI, blue) 20 min following irradiation. Reproduced with permission from [ 54 ] …”

Issues to Consider in Designing Immunotherapy Clinical Trials for Glioblastoma Management

“…There are a variety of other biomarkers potentially reflecting treatment response in a variety of cancers [73]- [76]. In GBM specifically, a group found that phosphorylation of two transcription factors, STAT-1 and STAT-5, can delineate response to immunotherapy and dendritic cell vaccines [77].…”